Chang I-Chia, Lin Pei-Chun
Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan.
Bioinspir Biomim. 2023 Apr 6;18(3). doi: 10.1088/1748-3190/acc6ac.
We report on the development of separated and laterally arranged two-leg (SLTL) models with/without differentiated leg properties and their use as the dynamic running and turning templates for a hexapod robot. The laterally arranged two-leg morphology enables differential driving for turning. The differentiable leg settings, such as stiffness, enables the model to adopt unbalanced leg arrangements of empirical legged gaits, such as a tripod gait, into consideration. The fixed-point motion of the model was utilized as the main methodology to plan dynamic running and turning, in which the plot of one-step distance versus period was constructed for the legs' operation point selection and matching. The proposed methodology was experimentally validated using four indices: turning curvature, flight phase, motion stability, and energy efficiency. The experimental results show that the running robot using the SLTL model with differentiated leg stiffness has better energy efficiency than one without by 4%, while the latter model has identical performance to the original spring-loaded inverted pendulum model with rolling contact. As for turning, the robot using the SLTL models with/without differentiated leg stiffness can preserve dynamic turning in all experiments with turning curvatures up to0.28m-1and0.30m-1, respectively,33%and43%more than the robot using the original model-less phase-shift turning strategy (0.21 m-1). Using the proposed model-based strategy, the flight phase of the robot turning in all curvatures (including straight running) maintains around 20%, the root-mean-squared (RMS) values of pitch and roll remains less than3 deg, and the specific resistance (SR) is bounded between0.64 and 0.73. By contrast, the robot using the phase-shifting turning strategy can maintain dynamic motion up to a turning curvature of0.21 m-1. A further increase in phase shifting not only does not increase the turning curvature but also changes the robot motion from running to walking. In this case, no flight phase exists, theSRjumps up significantly, and RMS values of pitch and roll also increase dramatically. In short, the experimental validation confirms the effectiveness of the proposed methodology for initiating the dynamic running and turning of the robot.
我们报告了具有/不具有差异化腿部特性的分离式横向排列双腿（SLTL）模型的开发情况，以及它们作为六足机器人动态奔跑和转弯模板的应用。横向排列的双腿形态实现了转弯的差动驱动。可微分的腿部设置，如刚度，使模型能够考虑采用经验性腿部步态的不平衡腿部排列，如三脚架步态。模型的定点运动被用作规划动态奔跑和转弯的主要方法，其中构建了一步距离与周期的关系图，用于腿部操作点的选择和匹配。所提出的方法通过四个指标进行了实验验证：转弯曲率、飞行阶段、运动稳定性和能量效率。实验结果表明，使用具有差异化腿部刚度的SLTL模型的奔跑机器人比不具有该特性的机器人能量效率高4%，而后者的性能与具有滚动接触的原始弹簧加载倒立摆模型相同。至于转弯，使用具有/不具有差异化腿部刚度的SLTL模型的机器人在所有实验中都能保持动态转弯，转弯曲率分别高达0.28m⁻¹和0.30m⁻¹，比使用原始无模型相移转弯策略（0.21m⁻¹）的机器人分别高出33%和43%。使用所提出的基于模型的策略，机器人在所有曲率（包括直线奔跑）下转弯的飞行阶段保持在20%左右，俯仰和滚动的均方根（RMS）值保持在3°以下，比电阻（SR）在0.64至0.73之间。相比之下，使用相移转弯策略的机器人在转弯曲率达到0.21m⁻¹时仍能保持动态运动。相移的进一步增加不仅不会增加转弯曲率，还会使机器人的运动从奔跑变为行走。在这种情况下，不存在飞行阶段，SR会大幅跃升，俯仰和滚动的RMS值也会急剧增加。简而言之，实验验证证实了所提出的方法对于启动机器人动态奔跑和转弯的有效性。
